This invention relates to fluorescent lamps and fluorescent lamp phosphors. More particularly, this invention is concerned with the improved performance of fluorescent lamps which include manganese-activated zinc orthosilicate phosphor.
Manganese-activated zinc orthosilicate phosphor (Zn.sub.2 SiO.sub.4 :Mn) is a green-emitting phosphor. One of the problems associated with Zn.sub.2 SiO.sub.4 :Mn is its relatively poor fluorescent lamp performance and maintenance. Poor maintenance means that the light output, or lumens per watt, of the phosphor decreases to a greater extent during lamp life than is desirable. Because of its relatively poor fluorescent lamp maintenance, Zn.sub.2 SiO.sub.4 :Mn phosphor has been generally found to be unsuitable for use as a green-emitting phosphor in commercially available fluorescent lamps. Heretofore, commercially available fluorescent lamps which include green-emitting phosphors have typically employed expensive rare earth green-emitting phosphors, such as cerium terbium magnesium aluminate.
The importance of high-performance, green-emitting phosphors with low depreciation characteristics in fluorescent lamps has increased in recent years with the growing demand for high CRI performance lamps. For that reason a fluorescent lamp including a less expensive high-maintenance green-emitting phosphor is desirable.